Methods and systems for performing reliable asynchronous notification of high-level document operations

ABSTRACT

A mechanism is described for the reliable notification to client applications of the implementation of predefined high-level document commands in a database. The database management system is issued a number of high-level document commands such as “move electronic mail message” or “add folder” which are to be implemented in the underlying database. As each high-level document command is implemented, an entry representing the high-level document command is set in a notification table stored in a persistent memory such as the database. The appropriate notification is then dispatched to any subscribing client applications. The client application then acknowledges to the database application that the notification has been received. In response, the entry is deleted in the notification table in the database. If the database management system were to fail, the system would check the notification table to see what notification it should send upon restarting.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application ofcommonly-assigned U.S. patent application Ser. No. 09/680,045 filed Oct.4, 2000, entitled “Methods and Systems for Performing ReliableAsynchronous Notification of High-Level Document Operations” and whichis incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to the field of database managementsystems. In particular, the present invention relates to methods andsystems for performing reliable asynchronous notification of high-leveldocument operations in a database.

2. Background and Relevant Art

With the development of computer networks and the Internet, anyone whohas access to an Internet capable computer may access information fromall over the world. The present era has even been termed the“information age” due to the widespread abundance of information.Although this abundance of information is useful, individuals may easilybe overwhelmed with information to the point where it is difficult tofilter out relevant information from irrelevant information.

Database management systems are systems that manage collections of data(i.e., databases) so as to allow individuals, devices and applicationsto easily access, manage, and update information. Thus, databasemanagement systems provide a significant contribution to the informationage by allowing for the efficient use of information.

Conventional database management systems such as the database managementsystem 100 shown in FIG. 1 include an underlying database 110 thatcontains organized data in the form of a number of tables such as table“A”, table “B”, table “C” and table “D”. Each table contains entriesthat associate documents with properties of the documents. For example,one table may contain a count of the number of files within givenfolders, another may list the memory size of given files, yet anothermay list other properties associated with given files, or folders. Foreach document, there is typically more than one table that mayassociated with the document by, for example, describing properties ofthe document.

A document (e.g., document 1, 2, 3 and 4 in FIG. 1) is an identifiableentity from the viewpoint of applications that use the databasemanagement system. For example, a folder or an item such as anelectronic mail message within the folder may be considered to be adocument since they are identified as entities from the viewpoint of theapplication that uses the database management system. For example, inthe context of electronic messaging, an application may present folderssuch as “in-boxes” and “out-boxes” to a user with correspondingelectronic mail messages in the folders. These folders and electronicmail messages are “documents” from the viewpoint of the application.Similarly, files and directories within a file system may also bedocuments from the viewpoint of the application that uses the databasemanagement system. The tables within the underlying database are notconsidered to be documents since they are identified internal to thedatabase management system, and not at the higher level of theapplication that uses the database management system.

The database application 120 generates high-level document commands(e.g., high-level command 121) that relate to operations to be performedon a document. Examples of such document commands might includeoperations such as, for example, move folder, move message, deletemessage, copy folder, copy file, and so forth.

Each of these high-level document commands is received by the databaseengine 130 which implements the high-level document commands byexecuting a number of object commands that result in objects such astables being updated. Typically, the database engine would use the diskaccess module 140 (e.g., a disk driver) of an operating system toproduce the physical control signals necessary to read and write theappropriate sectors in the disk, each object comprising one or morepossibly discontiguous sectors on the disk.

It is often desirable for one client application to receive notificationwhen a high-level document command meeting certain criteria has beenimplemented by another client application. For example, if a clientapplication is viewing all electronic messages within a folder,notification when another client application adds a message to thefolder will allow the client application to refresh the display.

FIG. 2 illustrates a flowchart of a conventional method 200 forperforming notifications that certain high-level document commands havebeen implemented in the database. When receiving a given high-leveldocument command, the database management system first implements thecorresponding high-level document command in the database (act 201).Once implemented, the database management system determines whichapplications have subscribed to be notified when the given high-leveldocument command is implemented (act 202). The database managementsystem then dispatches a notification that the high-level documentcommand has been implemented (act 203).

The vast majority of the time, when a high-level document command havingcertain criteria is issued, the subscribing client applications areproperly notified of the high-level document command and thus canrespond appropriately. However, sometimes computer systems becomeinoperative due to system failures, corruption, power loss, or the like.In such cases, there is a possibility that the high-level documentcommand is implemented in the database, but that the subscribing clientapplication never receives notification of the implementation. Forexample, the client application may become inoperative and thus becomeunable to receive and interpret a notification that a certain high-leveldocument command has been implemented. Also, the database managementsystem itself may become inoperative so that although the command hasbeen implemented, no notification was ever dispatched.

Thus, conventional system contain no guarantee that the propernotifications of a high-level document command will always be dispatchedor received if a high-level document command is implemented. Therefore,what are desired are methods and systems for improving accuracy andreliability in notifying client applications that certain high-leveldocument commands have been implemented in a database.

BRIEF SUMMARY OF THE INVENTION

The principles of the present invention provide for the reliableasynchronous notification to client applications of the implementationof predefined high-level document commands that are implemented in adatabase managed by a database management system. These notificationsare “asynchronous” since the high-level document commands are actuallyimplemented in the database prior to sending the notification to clientapplications. Thus, the notified client applications do not affect theimplementation of the high-level document commands in the database.

The database management system is issued a number of high-level documentcommands which are to be implemented in the underlying database. Suchhigh-level document commands include high-level commands that relate toactions to be taken on documents such as folders, files, messages andother entities that are identified at the level of the application thatuses the database management system. For example, in electronicmessaging applications, one high-level document command may be to add amessage to a folder.

Ultimately, the database engine implements the high-level documentcommand by altering one or more tables in the database. However, beforeimplementing the high-level command, an entry is set in a notificationtable stored in a persistent memory such as the database. Alternatively,the entry in the notification table is set in the same transaction asany other table changes that are made to implement the high-levelcommand. In this transaction, either all actions in the transaction areperformed (all relevant tables are altered) or no actions in thetransaction are taken (none of the relevant tables are altered). Thus,if the entry in the notification table is set, then the correspondinghigh-level document command is guaranteed to have been implemented inthe database.

Ideally, the client application that requested notification and thedatabase management system will continue to be operational. In thisideal case, the notification that the given high-level document commandhas been implemented is dispatched to the client application. The clientapplication then acknowledges to the database management system that thenotification has been received. In response, the entry is deleted in thenotification table in the database. The notification may be resent ifthe database management system does not receive such acknowledgementwithin an expected time period.

To make sure that the client management system properly performs allactions responsive to the notification, the entry in the notificationtable may remain set until the database management system receivesacknowledgement from the client application that all necessary actionshave been performed by the client application. Thus, if a clientapplication fails while implementing any necessary actions responsive tothe notification, the notification will be resent to allow the clientapplication to re-perform any necessary actions once the clientapplication becomes operational again.

Suppose now that a system failure occurs at the database managementsystem after the high-level document command is implemented in thedatabase, but before notification is dispatched. Upon restarting thedatabase management system, the system will check the notification tableto see what notifications entries are set. These entries correspond tonotifications for which the database management system has not receivedacknowledgement from the client application. The database managementsystem then sends corresponding notifications to the client application.In this manner, the client application receives notification even if adatabase management system failure occurs.

Now suppose that the notification is indeed dispatched, but that theclient application has failed so as to be unable to receive thenotification. The database management system will not receiveacknowledgement from the client application. Therefore, the databaseapplication will resend the notification until the notification isacknowledged upon restarting the client application. In this manner, theclient application receives notification even if a client applicationfailure occurs.

Therefore, the principles of the present invention provide for areliable way of notifying client application when particular high-leveldocument commands are implemented in a database, the notificationssurviving even failure of the database management system or clientapplication.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by the practice of the invention. Thefeatures and advantages of the invention may be realized and obtained bymeans of the instruments and combinations particularly pointed out inthe appended claims. These and other features of the present inventionwill become more fully apparent from the following description andappended claims, or may be learned by the practice of the invention asset forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered to be limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIG. 1 illustrates a hierarchical view of a database management systemin accordance with the prior art;

FIG. 2 illustrates a flowchart of a method of notifying clientapplications when a particular high-level document command isimplemented in accordance with the prior art;

FIG. 3 illustrates an exemplary system that provides a suitableoperating environment for the present invention;

FIG. 4 illustrates a hierarchical view of a database management systemin accordance with the present invention in which notifications survivesystem failures;

FIG. 5 illustrates a flowchart of a method for guaranteeing notificationdespite intervening system failures; and

FIG. 6 illustrates a flowchart of a method for recovering from a systemfailure so as to ensure notification transmission.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention extends to both methods and systems for reliablynotifying client applications of the implementation of predefinedhigh-level document commands in a database management system. Thesenotifications are “asynchronous,” meaning that the client applicationsdo not affect the implementation of the high-level document commandsince the implementation takes place prior to the notification.

The notification occurs even if the database management system or theclient application experiences a system failure. A notification tablerecords implementation of high-level document commands. Then,notification is dispatched to the client applications that are to benotified. The client application then acknowledges at least receipt ofthe notification, and perhaps that they have completed performingactions in response to the notification. Upon receiving theacknowledgement, the notification table is updated to remove the recordof the high-level document command.

If the database management system or the client application experiencesa system failure that inhibits the notification process, thenotification is resent after restarting the failed system. Uponrestarting the database management system, for example, the databasemanagement system checks the notification table and resends anynotifications for which there is a record (i.e., notifications whichhave not been acknowledged). Therefore, the present invention providesfor the reliable notification of high-level document commands where thenotifications survive even system failures.

The embodiments of the present invention may comprise a special purposeor general purpose computer including various computer hardware, asdiscussed in greater detail below. Embodiments within the scope of thepresent invention also include computer-readable media for carrying orhaving computer-executable instructions or data structures storedthereon. Such computer-readable media can be any available media whichcan be accessed by a general purpose or special purpose computer. By wayof example, and not limitation, such computer-readable media cancomprise physical storage media such as RAM, ROM, EEPROM, CD-ROM orother optical disk storage, magnetic disk storage or other magneticstorage devices, or any other medium which can be used to carry or storedesired program code means in the form of computer-executableinstructions or data structures and which can be accessed by a generalpurpose or special purpose computer.

When information is transferred or provided over a network or anothercommunications connection (either hardwired, wireless, or a combinationof hardwired or wireless) to a computer, the computer properly views theconnection as a computer-readable medium. Thus, any such a connection isproperly termed a computer-readable medium. Combinations of the aboveshould also be included within the scope of computer-readable media.Computer-executable instructions comprise, for example, instructions anddata which cause a general purpose computer, special purpose computer,or special purpose processing device to perform a certain function orgroup of functions.

FIG. 3 and the following discussion are intended to provide a brief,general description of a suitable computing environment in which theinvention may be implemented. Although not required, the invention willbe described in the general context of computer-executable instructions,such as program modules, being executed by computers in networkenvironments. Generally, program modules include routines, programs,objects, components, data structures, etc. that perform particular tasksor implement particular abstract data types. Computer-executableinstructions, associated data structures, and program modules representexamples of the program code means for executing steps of the methodsdisclosed herein. The particular sequence of such executableinstructions or associated data structures represent examples ofcorresponding acts for implementing the functions described in suchsteps.

Those skilled in the art will appreciate that the invention may bepracticed in network computing environments with many types of computersystem configurations, including personal computers, hand-held devices,multi-processor systems, microprocessor-based or programmable consumerelectronics, network PCs, minicomputers, mainframe computers, and thelike. The invention may also be practiced in distributed computingenvironments where tasks are performed by local and remote processingdevices that are linked (either by hardwired links, wireless links, orby a combination of hardwired or wireless links) through acommunications network. In a distributed computing environment, programmodules may be located in both local and remote memory storage devices.

With reference to FIG. 3, an exemplary system for implementing theinvention includes a general purpose computing device in the form of aconventional computer 320, including a processing unit 321, a systemmemory 322, and a system bus 323 that couples various system componentsincluding the system memory 322 to the processing unit 321. The systembus 323 may be any of several types of bus structures including a memorybus or memory controller, a peripheral bus, and a local bus using any ofa variety of bus architectures. The system memory includes read onlymemory (ROM) 324 and random access memory (RAM) 325. A basicinput/output system (BIOS) 326, containing the basic routines that helptransfer information between elements within the computer 320, such asduring start-up, may be stored in ROM 324.

The computer 320 may also include a magnetic hard disk drive 327 forreading from and writing to a magnetic hard disk 339, a magnetic diskdrive 328 for reading from or writing to a removable magnetic disk 329,and an optical disk drive 330 for reading from or writing to removableoptical disk 331 such as a CD-ROM or other optical media. The magnetichard disk drive 327, magnetic disk drive 328, and optical disk drive 330are connected to the system bus 323 by a hard disk drive interface 332,a magnetic disk drive-interface 333, and an optical drive interface 334,respectively. The drives and their associated computer-readable mediaprovide nonvolatile storage of computer-executable instructions, datastructures, program modules and other data for the computer 320.Although the exemplary environment described herein employs a magnetichard disk 339, a removable magnetic disk 329 and a removable opticaldisk 331, other types of computer readable media for storing data can beused, including magnetic cassettes, flash memory cards, digital videodisks, Bernoulli cartridges, RAMs, ROMs, and the like.

Program code means comprising one or more program modules may be storedon the hard disk 339, magnetic disk 329, optical disk 331, ROM 324 orRAM 325, including an operating system 335, one or more applicationprograms 336, other program modules 337, and program data 338. A usermay enter commands and information into the computer 320 throughkeyboard 340, pointing device 342, or other input devices (not shown),such as a microphone, joy stick, game pad, satellite dish, scanner, orthe like. These and other input devices are often connected to theprocessing unit 321 through a serial port interface 346 coupled tosystem bus 323. Alternatively, the input devices may be connected byother interfaces, such as a parallel port, a game port or a universalserial bus (USB). A monitor 347 or another display device is alsoconnected to system bus 323 via an interface, such as video adapter 348.In addition to the monitor, personal computers typically include otherperipheral output devices (not shown), such as speakers and printers.

The computer 320 may operate in a networked environment using logicalconnections to one or more remote computers, such as remote computers349 a and 349 b. Remote computers 349 a and 349 b may each be anotherpersonal computer, a server, a router, a network PC, a peer device orother common network node, and typically include many or all of theelements described above relative to the computer 320, although onlymemory storage devices 350 a and 350 b and their associated applicationprograms 336 a and 336 b have been illustrated in FIG. 3. The logicalconnections depicted in FIG. 3 include a local area network (LAN) 351and a wide area network (WAN) 352 that are presented here by way ofexample and not limitation. Such networking environments are commonplacein office-wide or enterprise-wide computer networks, intranets and theInternet.

When used in a LAN networking environment, the computer 320 is connectedto the local network 351 through a network interface or adapter 353.When used in a WAN networking environment, the computer 320 may includea modem 354, a wireless link, or other means for establishingcommunications over the wide area network 352, such as the Internet. Themodem 354, which may be internal or external, is connected to the systembus 323 via the serial port interface 346. In a networked environment,program modules depicted relative to the computer 320, or portionsthereof, may be stored in the remote memory storage device. It will beappreciated that the network connections shown are exemplary and othermeans of establishing communications over wide area network 352 may beused.

FIG. 4 illustrates a database management system 400 in accordance withthe present invention. Although, not required, the database managementsystem 400 may be implemented in the computing environment shown in FIG.4. In contrast to the prior art database management system shown in FIG.1, the database management system 400 includes a notification table 450.The operation of the database management system 400 of FIG. 4 will bedescribed with respect to the method 500 illustrates in FIG. 5.

FIG. 5 shows a flowchart of a method performed by the databasemanagement system 400 to perform reliable notification when a high-leveldocument command is implemented by the database management system. Thedatabase application 420 issues a high-level document command 421 to thedatabase engine 430. This high-level document command is for performinga function on a document that the database application recognizes to bea separately identifiable entity. For example, if the databasemanagement system supports electronic mail applications, the documentmay be an electronic mail message or a folder that contains theelectronic mail message. Typical operations might be to move, delete,copy, update, or add a new document.

As the database engine 430 receives each high-level document command,the database engine implements the high-level document command in thedatabase 410 (act 501). Typically, implementing a high-level documentcommand in the database may involve changing entries in a number oftables such as tables “A”, “B”, “C” and “D” since each table couldpotentially have an entry for the corresponding document. The clientapplication that uses the database management system 400 is typicallynot concerned with the details of which table needs to be changed. Thedatabase engine implements those details usually unbeknownst to theclient application that generated the high-level document command.Highly reliable database engines typically perform changes to the tablesin a transacted manner so that either all the table changes for theparticular high-level document command are made, or none of the tablechanges are made.

In addition to implementing the high-level document command in thedatabase (act 501), embodiments within the scope of the presentinvention also include a means or step for ensuring a correspondingnotification about the high-level document command is preserved until atleast one client application acknowledges the notification. In theembodiment illustrates in FIG. 5, this may be accomplished by performingthe remaining acts of the method 500.

For example, in addition to implementing the high-level document command(act 501), the database engine alters the notification table 450 toreflect that the high-level document command has been implemented (act502). This may be performed after the high-level document command isimplemented. However, it is preferred that the notification table bechanged atomically with the other tables involved with implementing thehigh-level document command so that either all the table are changedtogether or no changes are made at all. This may be accomplished byhaving the database engine implement, in a single transaction, thenotification table update along with all other table updates needed toimplement the high-level document command. If the notification table andthe other relevant tables are updated in the same transaction, there ishigh assurance that the notification table accurately reflects that thehigh-level document command actually was implemented in the database.

The database management system also identifies any client applicationsthat should be notified of the high-level document command (act 503).Typically, this might involve determining which client application aresubscribers to the high-level document command although this is notrequired. A client application could be notified by default withouthaving subscribed or perhaps a third party client application hasdirected the other client application to receive notifications of theimplementation of certain high-level document commands.

Once the client applications to be notified are identified (act 503), anotification that the high-level document command has been implementedin then dispatched to the identified client applications (act 504).Messaging may be employed to dispatch the notification as when thedatabase management system and the client application to be notified donot reside on the same machine. Alternatively, function calls through anapplication program interface or through other interfaces may beemployed when the database management system and the client applicationreside on the same machine.

Once notified, the client application may then perform any number andvariety of processes in response to receiving the notification. Forexample, if the original client application has added a new electronicmail message to a public folder, each of the client applications havingaccess to the public folder may be notified. If the client applicationis already displaying the public folder, the client application wouldthen refresh a display to reflect the addition.

Ultimately, the database management system receives acknowledgement backfrom the client application that received the notification (act 505).The client application may return this acknowledgement as soon as theclient application receives notification. However, it may often bebeneficial to return acknowledgement well after this time as soon as theclient application has completed performing any processes in response toreceiving notifications. This ensures that the client application hassuccessfully completed its purpose in being notified in the first place.

Once the database management system receives acknowledgement back fromthe client application (act 505), the database management system altersthe notification table 450 to delete reference to the implementation ofthe high-level document command (act 506). Thus, the notification tablereflects the implementation of every high-level document command thathas been implemented in the database, but for which the databasemanagement system has not yet received acknowledgement back from theclient application. In this way, the notification table reflects thosenotifications that should have been sent to the client application, butfor which the notification success is uncertain.

As will now be described, this method permits for notifications of theimplementation of high-level document commands to survive even systemfailures. For example, suppose that, for whatever reason, the high-leveldocument command is implemented in the database, but the appropriatenotification is never dispatched. Perhaps the database management systemexperiences a failure after the high-level document command wasimplemented, but before the database management system actually sent thenotification. In this case, at least the database management systemwould have set the appropriate entries in the notification table toreflect that the high-level document command was implemented.

FIG. 6 illustrates a flowchart of method 600 of how the databasemanagement system would recover from such a failure and send theappropriate notification. Upon restarting the database management system(act 601), the database management system checks the notification tableto identify any high-level document commands that were implemented, butfor which there has not yet been acknowledgement back from the clientapplication (act 602). If there are none (NO in decision block 602),then no notification needs to be resent and the method ends. If thereare some (YES in decision block 602), then the subscribers to thenotification are identified (act 603), and the appropriate clientapplications are notified (act 604). Upon receiving acknowledgement backfrom the client applications (act 605), the appropriate entry in thenotification table is cleared (act 606). Thus, even a failure of thedatabase management system will not prevent appropriate notification.

Furthermore, if, for some reason, the notification was sent, but theclient application never received notification, the client applicationwill still be notified. For example, suppose that the machine hostingthe client application was to fail, or perhaps the notification medium(e.g., a network) was to fail resulting in the client application notreceiving the notification. In this case, the client application wouldnot return an acknowledgement and the entry would remain in thenotification table. The database management system may be configured tocontinue to send the notification on a periodic basis absent anacknowledgement until acknowledgement is finally returned. Thus,notification may even be made if the client application or networkshould fail.

Thus, the principles of the present invention provide for a reliable wayof notifying client applications when a particular high-level documentcommand is implemented in a database. The present invention may beembodied in other specific forms without departing from its spirit oressential characteristics. The described embodiments are to beconsidered in all respects only as illustrative and not restrictive. Thescope of the invention is, therefore, indicated by the appended claimsrather than by the foregoing description. All changes which come withinthe meaning and range of equivalency of the claims are to be embracedwithin their scope.

1. A method for providing reliable notification of the implementation ofhigh-level document commands to client applications in a system thatincludes an operating system, client applications, a database and adatabase engine that receives and implements the high-level documentcommands, wherein the method is performed in such a way that thenotification survives even failures of either the database engine orclient applications, the method comprising: receiving at a clientapplication, notification of the implementation of one or morehigh-level document commands, wherein the notification is generated bythe database engine in response to receiving and implementing the one ormore high-level document commands, wherein the notification is onlyissued to the client application subsequent to creating an entry in apersistently stored notification table to reflect implementation of theone or more high-level document commands in the database; upon receivingthe notification, the client application sending acknowledgment of thenotification to the system, wherein the client application only sendsacknowledgement of the notification upon first performing actionscorresponding to the implementation of the one or more high-leveldocument commands, and such that the system only receivesacknowledgement of the notification upon the client application firstperforming said actions; and wherein the notification table is updatedto indicate that the client application no longer needs to be sent thenotification after the acknowledgment is received by the system.
 2. Amethod as recited in claim 1, wherein the method further includesreceiving the notification a plurality of times prior to sending theacknowledgement.
 3. A method as recited in claim 1, wherein the clientapplication fails subsequently to receiving the notification and priorto sending the acknowledgement, and wherein the notification is sent tothe client application subsequent to the client application failing andupon becoming operational again, such that the client application isable to send the acknowledgement.
 4. A method as recited in claim 1,wherein the notification table is stored in the database.
 5. A method asrecited in claim 1, wherein implementing the high-level document commandand altering the persistently stored notification table to reflect theimplementation occur in a single transaction of the database engine. 6.A method as recited in claim 1, wherein implementing the high-leveldocument command in the database comprises an act of moving a document.7. A method as recited in claim 1, wherein implementing the high-leveldocument command in the database comprises an act of deleting adocument.
 8. A method as recited in claim 1, wherein implementing thehigh-level document command in the database comprises an act of copyinga document.
 9. A method as recited in claim 1, wherein implementing thehigh-level document command in the database comprises an act of adding adocument.
 10. A method as recited in claim 1, wherein implementing thehigh-level document command in the database comprises an act of updatinga document.
 11. A computer program product comprising one or morecomputer-readable media having computer-executable instructions forimplementing a method for providing reliable notification of theimplementation of high-level document commands to client applications ina system that includes an operating system, client applications, adatabase and a database engine that receives and implements thehigh-level document commands, wherein the method is performed in such away that the notification survives even failures of either the databaseengine or client applications, wherein the method comprises: receivingat a client application, notification of the implementation of one ormore high-level document commands, wherein the notification is generatedby the database engine in response to receiving and implementing the oneor more high-level document commands, wherein the notification is onlyissued to the client application subsequent to creating an entry in apersistently stored notification table to reflect implementation of theone or more high-level document commands in the database; upon receivingthe notification, the client application sending acknowledgment of thenotification to the system, wherein the client application only sendsacknowledgement of the notification upon first performing actionscorresponding to the implementation of the one or more high-leveldocument commands, and such that the system only receivesacknowledgement of the notification upon the client application firstperforming said actions; and wherein the notification table is updatedto indicate that the client application no longer needs to be sent thenotification after the acknowledgment is received by the system.
 12. Acomputer program product as recited in claim 11, wherein the methodfurther includes receiving the notification a plurality of times priorto sending the acknowledgement.
 13. A computer program product asrecited in claim 11, wherein the client application fails subsequentlyto receiving the notification and prior to sending the acknowledgement,and wherein the notification is sent to the client applicationsubsequent to the client application failing and upon becomingoperational again, such that the client application is able to send theacknowledgement.
 14. A computer program product as recited in claim 11,wherein the notification table is stored in the database.
 15. A computerprogram product as recited in claim 11, wherein implementing thehigh-level document command and altering the persistently storednotification table to reflect the implementation occur in a singletransaction of the database engine.
 16. A computer program product asrecited in claim 11, wherein implementing the high-level documentcommand in the database comprises an act of moving or copying adocument.
 17. A computer program product as recited in claim 12, whereinimplementing the high-level document command in the database comprisesan act of deleting a document.
 18. A computer program product as recitedin claim 11, wherein implementing the high-level document command in thedatabase comprises an act of moving or copying a document.
 19. Acomputer program product as recited in claim 11, wherein implementingthe high-level document command in the database comprises an act ofadding a document.
 20. A computer program product as recited in claim11, wherein implementing the high-level document command in the databasecomprises an act of updating a document.